<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>arguments</title>
</head>
<body>
    <script>
    var  yh=prompt(("请输入用户名"));
    var mm=prompt(('请输入密码'));
    var yzm=prompt(('请输入验证码'));
    function login(){
        if(isNaN(mm)){
            alert('密码错误')
        }
        if(yzm.length<4){
            alert('验证码不小于4位')
        }
    }
        login(yh,mm,yzm);
    console.log();
    
    </script>
</body>
</html>